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pngout: does not remove tEXt chunk if it does not also reduce IDAT

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• caveman at 2010-03-02 10:50
  Hello,
  I have a file produced by Adobe ImageReady and apparently pngout is not able to reduce it any further, the problem is that since it cannot reduce the overall file size it does not strip the tEXt chunk:
  pngout -v wont-remove-chunk.png
                  Name  Offset  Length    CRC
  Required chunk: IHDR 00000010 0000000d 017365fa
    Remove chunk: tEXt 00000029 00000019 71c9653c
  Required chunk: IDAT 0000004e 000029df b71836bb
  Required chunk: IEND 00002a39 00000000 ae426082
  
  In:  10813 bytes              wont-remove-chunk.png /c2 /f5
  Out:                            wont-remove-chunk.png /c2 /f5
  Block boundaries: none (1 block)
  
  Out:  14150  -2836.7=  11313.2
  Out:  11317    -28.0=  11289.0
  Out:  11260    -14.5=  11245.5
  Out:  11219    -20.2=  11198.7
  Out:  11184    -38.8=  11145.1
  Out:  11091    -15.3=  11075.6
  Out:  11066    -10.7=  11055.2
  Out:  11015    -1.5=  11013.5
  Out:  11015    -0.2=  11014.7
  Out:  11014 bytes             
  Took 0.399 sec.
  
  Unable to compress further
  
  I know I could force pngout to write the bigger file but I would loose the smaller IDAT chunk, is there a way to remove the tEXt chunk and keep the existing IDAT chunk? (without using another tool).
  And what would have happen if pngout had produced a slightly larger IDAT chunk compared to the actual one, but a smaller overall file size due to the chunk removal?
• Awesoken at 2010-03-05 02:45

  Re: pngout: does not remove tEXt chunk if it does not also reduce IDAT

  I do not intend to make PNGOUT into a full blown chunk editor. Please use TweakPNG for that. The existing ability to edit chunks (at least sometimes) should be considered bonus.